All solid state non-volatile memory devices that are known to the inventors, including Flash memory, MultiMedia Card (MMC), and Subscriber Identity Module (SIM), are vulnerable to an abrupt termination of power. As but one example, a file-control system or the memory contents can be corrupted if the power-off occurs during a write sequence, such as during a file-control table update procedure. While this problem can exist in any electronic system that incorporates one or more non-volatile memory devices, the problem is especially acute in handheld portable electronic systems that are subject to frequency handling by the user. Examples of such systems include, but are not limited to, cellular telephones, personal digital assistants (PDAs), portable computers, image capture devices such as digital cameras, gaming devices, music appliances and handheld units or terminals that incorporate combinations of two or more such functions.
The abrupt and unexpected interruption of power can occur when the terminal is dropped due to one or more of a number of occurrences. For example, dropping the terminal can result in the movement or expulsion of the battery, leading to an abrupt and uncontrolled power-off condition. Dropping the terminal may also result in the movement or expulsion of the memory component itself, such as a plug-in memory card. This can also lead to an abrupt and uncontrolled power-off condition, as well as an abrupt termination of the memory component digital input outlines and the signals conveyed thereby.
It is known in the art to provide some protection for rotating magnetic media (a hard disk drive, or HDD). For example, U.S. Pat. No. 5,982,573, entitled “Disk Drive and Method for Minimizing Shock-induced Damage”, describes a disk drive having a fall detection control system that detects when the disk drive is in a free fall, and takes precautionary protective action to minimize physical damage from any resulting shock upon impact. The disk drive includes an accelerometer device that measures acceleration of the disk drive along three mutually orthogonal axes x, y, and z, and resolves the measurement into respective vectors. A processor is programmed to compute a net acceleration of the disk drive, compare the net acceleration with a selected acceleration threshold level, measure a duration that the net acceleration exceeds the acceleration threshold level, compare the measured duration with a selected reference time period, and output a warning signal when the measured duration exceeds the reference time period. Upon receipt of the warning signal, a controller initiates protective routines in preparation for shock.
Also of interest is U.S. Pat. No. 6,567,709, “Integrated Monitoring, Diagnostics, Shut-down and Control System”; U.S. Pat. No. 5,991,114 “Disc Drive Having Gram Load Reducer and Method of Operating Gram Load Reducer”, and U.S. Pat. No. 5,227,929, “Portable Computer Hard Disk Protective Reflex System”.
Prior to this invention, the inventors are not aware of any protective mechanisms or methods for solid state memory devices to avoid data corruption due to an impact after a fall.